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Old 11-14-2011, 02:40 PM   #1 (permalink)
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Vehicle: 1999 E320 (140k), 1995 SL500 (72k)
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1990 300E Fuel pumps test and replace

1990 300E with 200K on it. After 10 to 15 minutes, will start to miss and then stalls. Will not restart for several hours. The shop now says it needs both fuel pumps. To start with, should I hear the pumps run when the key is first turned on? Should they cycle or keep running? If I don't hear anything, should I start with volume and pressure tests and then change the filter? Or should I start with electrical checks at the pumps? Should the pumps always be changed as a pair? Thanks.

Last edited by yando51; 12-14-2011 at 02:59 PM.
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Old 11-14-2011, 03:09 PM   #2 (permalink)
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You may have posted this in the wrong forum section. A '97 E320 is a W210, however the following W124 troubleshooting technique may or may not apply to yours as well

The chances of both pumps dying at the exact same time are about slim to none. However, the mileage is about right for pump replacement if they're still the factory installed units.

I'd replace fuel relay & OVP relay first. Also replace all fuses with the updated type, cheap at less than $5 for the whole fuses kit that covers the whole car.

You should hear a faint but constant buzzing noise coming from the pumps while the engine is running. If the buzzing is erractic, inconsistent then there is a problem at the pumps. Check for voltage at the pumps with a helper turning the ignition key.

If the pumps look old & tired, replace both with new Bosch units and also install a new Bosch fuel filter while you have everything apart.

Be sure to use new copper crush washers, otherwise you are guaranteed to have a fuel leak.

Last edited by sbaert; 11-14-2011 at 03:17 PM.
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Old 12-14-2011, 03:12 PM   #3 (permalink)
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Update: Replaced both fuel pumps, fuel filter, fuel pressure regulator, checked fuel accumulator, replaced crank position sensor. After 10 to 15 minutes of running it starts to miss and then stalls, will not restart for hours. It does have battery voltage to fuel pumps while stalling and cranking.
While dead it has spark at the plugs and power to the fuel pumps. Disconnected fuel line to fuel distributor, held thumb over line, cycled key and it sprayed gas. Tried starting fluid but still no fire?
This system has the fuel pump relay as part of the MAS. Are there other systems controlled by the MAS and OVP that can cause stall and no restart? Thanks

Last edited by yando51; 12-14-2011 at 03:25 PM.
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Old 12-17-2011, 12:33 PM   #4 (permalink)
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b

Sounds like temperature related if it takes hours to restart. Ignition coils fail with age and heat. No spark with all that fuel youre getting to the cylinders? What's the state of your ignition system? Voltage regulator worn out? Wires failing? Etc... thermoswitches may be shot. I think there are two. Maybe something is shutting down signals to the ECU. With all you've done to the fuel system make sure the other systems are good (did you change/check the EHA at the fuel distributor?).
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Old 12-17-2011, 07:32 PM   #5 (permalink)
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i had a 300e with exact same simptoms... it was the vopr, as hinted at in the first reply
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Old 12-17-2011, 09:38 PM   #6 (permalink)
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Dam! sounds exactly what mine does.haven't started working on it yet ,so keep up the posts, sound like you've replaced lots of parts and still have the same problem.thru my research seems like the Mass relay behind the battery may be at fault.has the fuel pump relay and a/c compressor relay in it.that's what you can test next ,there a procedure for it here some where ,think in the diy fix's.anyhoo that's what I'm going to work on first on mine. it starts great drive for 10 or 15 min then stumbles and dies,try to restart and wont,let it sit for 1/2 hr and fires right up! freaking strange! electronically that mass relay is 1st in line,I guess it works fine when cold, then heats up and cold solder joints start to fail,cools down and fires right up. expansion and contraction
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Old 12-18-2011, 11:59 AM   #7 (permalink)
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Quote:
Originally Posted by nick.ged View Post
i had a 300e with exact same simptoms... it was the vopr, as hinted at in the first reply
+1.

If you don't have a record of the OVP ever being replaced, you should buy a new one for your high mileage 21 y.o. car just on principal. $50 run insurance.
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Old 12-18-2011, 02:03 PM   #8 (permalink)
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OVP won't cause a non-start. I'll just make everything bitch and moan. As for the advice above, it should be replaced regardless of the issue you currently have if you have no history.

Your issue is probably more related with fuel pressure.
How did you "check" the accumulator? If it wasn't a fuel pressure test that achieved greater than 2.8bar for 30mins, you need to do this to rule it off.

As for pumps, did you replace the check valves too (usually they come with the pumps, but I don't like to assume).
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Old 12-18-2011, 02:31 PM   #9 (permalink)
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The fuel accumulator was chedked by removing the hose and cycling the key with no fuel flowing back through it.
The new fuel pumps came with new check valves (Bosch pumps from NAPA auto parts for $140 each).
The fuel pressure regulator was exchanged from a known vehicle with no change in performance.
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Old 12-18-2011, 02:48 PM   #10 (permalink)
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As for the MAS, since the vehicle acts up within 15 minutes, I put a meter on the fuel pumps and monitored them while it started to miss and then stalled and would not restart. They had 13 volts which rules out the fuel pump relay in the MAS. I do not know what else the MAS controls? That info would be helpful for diagnosis.
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